Plank Jack
What Is the Plank Jack?
Plank Jack is a compound exercise that primarily targets the core and also engages the shoulders, chest and hip muscles. It is a beginner-level movement that holds a high plank while the feet jump out to a wide stance and back together, rep after rep, like a Jumping Jack performed with the upper body in a plank.
Its main job is conditioning work that doubles as anti-rotation core training. Because the hands stay planted and only the legs move, the trunk has to resist rocking from side to side and sagging at the hips while the feet jump, which is a different demand than a static hold. The jumping tempo also raises the heart rate, so the exercise shows up in bodyweight circuits, HIIT blocks and core finishers rather than as a standalone strength movement.
The abs and obliques work isometrically throughout to keep the hips level and square to the floor as the legs swing apart and together. The gluteus medius and the adductors on the inner thigh drive the jump itself, pulling the legs out and back in, while the shoulders, chest and serratus anterior keep the plank from collapsing under the added motion. Landing on a wider or narrower stance changes how far the hips have to travel, but the core's job of staying still does not change.
Plank Jack suits beginners who already own a steady Plank and want to add a conditioning element without new equipment. Anyone whose hips bounce or sag when they jump should regress to stepping the feet out and in one at a time until the trunk can hold still at speed. The Mountain Climber trains a similar plank-and-leg-drive pattern and is a natural next step once Plank Jack feels controlled.
Muscles Worked
- External Oblique
- Primary
- Rectus Abdominis
- Primary
- Deltoid
- High
- Gluteus Medius
- High
- Adductor Longus
- Medium
- Pectoralis Major
- Medium
- Serratus Anterior
- Medium
- Tensor Fasciae Latae
- Medium
Instructions
- Start in a high plank with your hands flat on the floor directly under your shoulders, arms straight.
- Set your feet together and form a straight line from head to heels, with your abs braced.
- Keeping your hands planted, jump both feet out to a wide stance, letting your hips lift only slightly as your feet leave the floor.
- Land softly on the balls of your feet and let your hips settle back level with your shoulders.
- Jump both feet back together to return to the starting plank position.
- Keep your shoulders stacked over your hands and your gaze down throughout each jump.
- Repeat at a controlled pace for the set, slowing down if your hips start to sway.
Common Mistakes
Hips Bouncing or Piking
Piking the hips high or letting them drop with each jump, instead of returning level after a small lift, takes the work off the core and loads the lower back.
Hands Too Far Forward
Letting the shoulders drift ahead of the hands puts the wrists and shoulders in a weaker, more strained position.
Landing Hard with Locked Knees
Slapping the feet down with straight knees sends impact up into the ankles and knees instead of absorbing it softly.
Outpacing Trunk Control
Jumping faster than the core can stabilize is the main cause of sagging or swaying hips, so speed should drop as soon as the plank starts to move.
Narrow or Uneven Jumps
Barely widening the stance, or landing one foot wider than the other, cuts the hip movement short and loads the sides of the trunk unevenly.
Injuries
Plank Jack is a low risk exercise when performed with proper technique. The wrists carry a large share of body weight in extension, so they take the most strain, followed by the shoulders when the hands drift ahead of them. The lower back is the other common strain point, loaded when the hips sag or bounce as the feet land.
Keep the hands directly under the shoulders, brace the abs before jumping, and land softly on the balls of the feet without letting the hips bounce. Warm up the wrists and shoulders first, and slow the tempo as soon as the hips start to sway or sag.
To regress, step the feet out and in one at a time instead of jumping, or elevate the hands on a bench to take load off the wrists. A steady Plank builds the trunk control the movement needs. To progress, increase the tempo or work interval while keeping the hips still, or move on to the Mountain Climber.
Stop if the wrists, shoulders or lower back start to hurt, or if the hips can no longer stay level with the shoulders. Use the hands-elevated or step-out version while a wrist, shoulder or lower back issue settles.
- Equipment
- Body weight
- Modality
- Cardio
- Difficulty
- Beginner
Alternative Exercises
Frequently Asked Questions
- Q: How is a Plank Jack different from a Mountain Climber?
A Mountain Climber drives one knee at a time toward the chest underneath the body, while a Plank Jack keeps the legs straighter and jumps them out to the side and back, closer to a Jumping Jack done in a plank. Both train the trunk to resist movement while the legs work.
- Q: Is Plank Jack a strength exercise or cardio?
It is mainly conditioning work with a core-stability demand layered on top. The jumping tempo raises the heart rate like a cardio drill, while the trunk has to isometrically resist rocking and sagging the entire set, which is why it is usually programmed by time rather than for heavy loading.
- Q: Can beginners do Plank Jacks?
Yes, as long as a steady Plank is comfortable first. Anyone whose hips bounce or sag when jumping should step the feet out and in one at a time instead, which keeps the same position without the landing impact.
- Q: How many Plank Jacks should I do?
Plank Jacks are usually programmed for time, such as 20 to 30 seconds of work with equal or longer rest, or as sets of 10 to 20 controlled reps inside a circuit. Stop the set as soon as the hips can no longer stay level.
- Q: How does Plank Jack compare to a regular Plank?
A regular Plank is a static hold, while Plank Jack adds continuous leg movement and a cardio demand on top of the same core-stability challenge. If the hips sway or sag during the jump, build a steady static hold first.